Transient Analysis of Partial Thermal Characteristics of Multistructure Power LEDs

Wang, Chien‐Ping; Chen, Tzung-Te; Fu, Han-Kuei; Chang, Tien-Li; Chou, Pei-Ting

doi:10.1109/ted.2013.2252903

Cited by 22 publications

(9 citation statements)

References 18 publications

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“…Hence, the TIM for the LED on FR4 underwent relatively lower thermal stress than that of the MCPCB. In addition, the large CTE mismatch resulted in delamination at the interface and a high concentration of thermal stress (Nishimura et al, 1989), which caused an increase in contact R th at the interface (Wang et al, 2013). This means that a negligible CTE between two surfaces has the potential for enhancing the reliability and thermal management of microelectronic devices (Permal et al, 2018).…”

Section: Resultsmentioning

confidence: 99%

Impact of thermal interface material on luminous flux curve of InGaAlP low-power light-emitting diodes

Raypah

Devarajan

Mahmud

2021

SSMT

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Purpose One major problem in the lighting industry is the thermal management of the devices. Handling of thermal resistance from solder point to the ambiance of the light-emitting diode (LED) package is linked to the external thermal management that includes a selection of the cooling mode, design of heatsink/substrate and thermal interface material (TIM). Among the significant factors that increase the light output of the of the LED system are efficient substrate and TIM. In this work, the influence of TIM on the luminous flux performance of commercial indium gallium aluminium phosphide (InGaAlP) low-power (LP) LEDs was investigated. Design/methodology/approach One batch of LEDs was mounted directly onto substrates which were glass-reinforced epoxy (FR4) and aluminium-based metal-core printed circuit boards (MCPCBs) with a dielectric layer of different thermal conductivities. Another batch of LEDs was prepared in a similar way, but a layer of TIM was embedded between the LED package and substrate. The TIMs were thermally conductive epoxy (TCE) and thermally conductive adhesive (TCA). The LED parameters were measured by using the integrated system of thermal transient tester (T3Ster) and thermal-radiometric characterization of LEDs at various input currents. Findings With the employment of TIM, the authors found that the LED’s maximum luminous flux was significantly higher than the value mentioned in the LED datasheet, and that a significant reduction in thermal resistance and junction temperature was revealed. The results showed that for a system with low thermal resistance, the maximum luminous flux appeared to occur at a higher power level. It was found that the maximum luminous flux was 24.10, 28.40 and 36.00 lm for the LEDs mounted on the FR4 and two MCPCBs, respectively. After TCA application on the LEDs, the maximum luminous flux values were 32.70, 36.60 and 37.60 lm for the FR4 and MCPCBs, respectively. Moreover, the findings demonstrated that the performance of the LED mounted on the FR4 substrate was more affected by the employment of the TIM than that of MCPCBs. Research limitations/implications One of the major problems in the lighting industry is the thermal management of the device. In many low-power LED applications, the air gap between the two solder pads is not filled up. Heat flow is restricted by the air gap leading to thermal build-up and higher thermal resistance resulting in lower maximum luminous flux. Among the significant factors that increase the light output of the LED system are efficient substrate and TIM. Practical implications The findings in this work can be used as a method to improve thermal management of LP LEDs by applying thermal interface materials that can offer more efficient and brighter LP LEDs. Using aluminium-based substrates can also offer similar benefits. Social implications Users of LP LEDs can benefit from the findings in this work. Brighter automotive lighting (signalling and backlighting) can be achieved, and better automotive lighting can offer better safety for the people on the street, especially during raining and foggy weather. User can also use a lower LED power rating to achieve similar brightness level with LED with higher power rating. Originality/value Better thermal management of commercial LP LEDs was achieved with the employment of thermal interface materials resulting in lower thermal resistance, lower junction temperature and brighter LEDs.

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Section: Resultsmentioning

confidence: 99%

Impact of thermal interface material on luminous flux curve of InGaAlP low-power light-emitting diodes

Raypah

Devarajan

Mahmud

2021

SSMT

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“…conversion efficiency of high-power LEDs is 20% and up to 80% of energy is released as heat [2]. The problem of heat dissipation restricts the development of high-power LEDs [3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Electrothermal Collaborative Cooling With Delayed Power Rail Switching Auxiliary Charging by Considering Energy Harvesting Mechanism for High-Power LEDs

Wang

Shen

Gao

et al. 2020

IEEE Trans. Compon., Packag. Manufact. Technol.

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With the development of high-power light-emitting diodes (LEDs), the heat flux density of devices has continued to increase, which in turn requires the development of increasingly effective methods of heat dissipation to control the working temperature of LEDs. Due to their impressive performance in solid refrigeration and energy harvesting, such thermoelectric devices as the thermoelectric cooler (TEC) and the thermoelectric generator (TEG) have been used to develop methods of heat dissipation that have been applied to power components and electronic devices. This paper proposes a delayed electro-thermal collaborative cooling system based on the TEC-TEG that uses the auxiliary charging technique for energy harvesting. In the designed delay circuit, two power source rails containing a TEG and a charged capacitor are switched automatically to supply energy to a TEC according to the charge of the capacitor and the discharge time of the delay circuit used for energy transmission. The results of experiments show that using our proposed scheme, the electromotive force can be increased by 21.6%, from 0.37 V to 0.45 V, in the TEG module compared with the collaborative electro-thermal cooling system without auto-delayed power rail switching. The switching time cost of the proposed system was only 0.8 s, and it could continuously supply enough electromotive force to drive the TEC and the overall cooling system. The proposed electro-thermal collaborative cooling system with delayed power rail switching and auxiliary charging can improve energy utilization and reduce device cost, which can help efficiently manage heat dissipation in high-power LEDs.

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“…This type of LED has a vertical structure that offers efficient heat dissipation, current spreading, and longterm reliability [18]. The LED package thermal resistance results from the die-attached layer (65%), chip (20%), and heat slug (15%) [19].…”

Section: Introductionmentioning

confidence: 99%

Research on dynamic thermal performance of high-power ThinGaN vertical light-emitting diodes with different submounts

Raypah¹,

Mahmud²,

Devarajan³

2020

Semicond. Sci. Technol.

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Investigation of dynamic thermal performance is a key to improve the heat management of high-power (HP) vertical light-emitting diodes (VLEDs). Specifically, the thermal time constant is a crucial parameter for optimizing the design and reliability of HP LEDs. Herein, the dynamic thermal behavior of seven HP ThinGaN VLEDs with different constructions was demonstrated. The LEDs’ thermal parameters were measured through the thermal transient tester system by a forward voltage technique. A three-stage of multiexponential function model was applied to divide the transient response curve into three regions with different thermal properties. This study focused on analyzing the first region that involved the chip region (epitaxial layer, wafer bonding layer, and submount) and chip bonding layer. The submounts of the LEDs under consideration include silicon carbide (SiC), silicon (Si), sapphire (Al2O3), and germanium (Ge). The results revealed that with a qualified wafer bonding layer, the LED packages with SiC, Si, and Al2O3 submount presented the optimum thermal time constant, which was 85, 69, 75, and 81 ms, respectively.

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Transient Analysis of Partial Thermal Characteristics of Multistructure Power LEDs

Cited by 22 publications

References 18 publications

Impact of thermal interface material on luminous flux curve of InGaAlP low-power light-emitting diodes

Impact of thermal interface material on luminous flux curve of InGaAlP low-power light-emitting diodes

Electrothermal Collaborative Cooling With Delayed Power Rail Switching Auxiliary Charging by Considering Energy Harvesting Mechanism for High-Power LEDs

Research on dynamic thermal performance of high-power ThinGaN vertical light-emitting diodes with different submounts

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